“Salt drive develops because sodium, while needed for many body functions in animals, is not a component of most forage plants. Salt drive is particularly evident in spring when ruminants begin foraging on fresh vegetation, but is often reduced or absent in winter. This relationship apparently stems from a greater intake of potassium concentrated in succulent vegetation that flushes sodium from mammalian systems; this leads to a temporary sodium imbalance that is satisfied by supplements of sodium, magnesium, and calcium. Interestingly, the vast bison herds roaming the western plains did not visit mineral licks, whereas their eastern counterparts followed well-worn trails to licks throughout the Appalachian Plateau. Western bison offset their sodium deficiencies by ingesting mineral-rich soils adhering to the short grasses in their diet.”